I have civicrm 4.6.5 running on Drupal 7.38 with the Mandrill 2 extension for bulk email.
I set up a webhook in mandrill to speak to civi and I sent a test bulk email (including fake email addresses) with mandrill to make sure it all works.
It all works fine except that Mandrill has been sending me 6 bounce notifications per ever since that email which included 1 fake email address.